Stem Neck Research Articles

Numerical analysis evaluation of artificial joints.

Artificial joints are exposed to loads on a daily basis. Loads on the bone through the artificial joint and the joint's sliding surface shear force may cause implant fixation failure, fatigue fractures, wear of the bearing and foreign body reactions. Artificial joints can experience sudden internal damage, which can be fatal if it occurs during activities performed at high altitudes or in water. The standard design hip prosthesis has a metal femoral stem. Most stem fractures are caused at the proximal one third of the stem by fatigue due to repetitive loading. Femoral stem neck fractures can also occur. To eliminate in vivo prosthesis failures, safety performance preclinical studies evaluate stem body and neck breakage. However, the development of new femoral stems via prototyping and fatigue test verification would require excessive time and money. Therefore, evaluation methods based on numerical analyses, such as finite element analysis (FEA), have been introduced to simulate tests on actual machines. Fatigue strength design verification using FEA can efficiently identify a design that can pass International Organization for Standardization fatigue tests. FEA may also aid with composite implant development by enabling efficient preclinical testing to prove safety using minimal actual fatigue testing. Once a biological safety study of a composite material is performed, a clinical trial can prove its clinical efficacy and safety and device regulatory approval can be requested. This review was created based on a translation of the Japanese review written in the Japanese Journal of Artificial Organs in 2020 (Vol. 49, No. 3, pp. 195-198), with adding some additional contents and references.

Translated article] Comparison of leg length discrepancy correction after the use of a modular neck stem and its monoblock homologue in total primary hip arthroplasty

Introduction and objectiveDual modularity stems seek to more precisely restore anatomy by allowing intraoperative adjustments thanks to modular necks. Our aim is to compare the radiographic length correction with the H MAX-M® Stem versus its monoblock counterpart H MAX-S®. Material and methodsA prospective cohort study was carried out through consecutive sampling on patients who underwent primary total hip arthroplasty with coxarthrosis diagnosis between 2011 and 2015. One arm of the cohort included patients who were operated with a modular stem and the other with a monobloc stem. Length was measured on the anteroposterior pelvic-bearing radiograph at 6 months. The mean of the measurements obtained for each arm of the cohort were compared with each other. ResultsNo statistically significant differences were observed in the correction of asymmetry between both groups, determined as the difference in length between the operated hip and the contralateral hip (p=.106). Nor were differences observed in postoperative length values (p=.053). It should be noted that for both the modular stem and the monobloc stem, the majority group is the one with restored length (84.1% and 80.4%, respectively; p=.001). ConclusionDespite the theoretical advantage of modularity and that having interchangeable parts could be of great interest, in our study, we have not been able to demonstrate a superiority of modular designs compared to monoblock for control of postoperative leg length discrepancy.

Abstract 5258: Mortality patterns among cancer survivors receiving care in dedicated survivorship clinics

Abstract Introduction: The number of deaths occurring among cancer survivors continues to be an outcome of concern. Our survivorship clinics provide risk stratification care for patients who have completed their curative treatment and are seen annually in a site-specific clinic. Here we describe mortality rates among adult patients receiving care in eleven site-specific survivorship clinics. Procedures: We conducted an analysis of 29,418 adult patients seen in our survivorship program from 2008-2021. Medical records were reviewed and categorized by each survivorship clinic. Eligibility criteria were: patients ≥18, treated for curative intent, completed their primary course of treatment, past the highest risk of recurrence, and transitioned based on site-specific survivorship algorithms. Descriptive statistics summarize the results. Results: There were 26475 survivors alive and 2943 deaths (Table 1). Of those alive, the greatest number were diagnosed with breast, genitourinary, and gastrointestinal malignancies. Death rates ranged from 2% to 38%, with the highest percent in stem cell transplant, head and neck, and gynecology malignancy survivors. 29% of deceased patients had died within one year of their transition from oncology care to survivorship clinics. Conclusions: Our results indicate differences in mortality risk among different cancer survivors; those who received transplants or were diagnosed with gynecologic or head/neck cancers had higher death rates. Survivors in these groups have short and long-term health risks which may require more proactive care. Current analyses are underway on the cause of death among patients who passed away within the first year of the transition to survivorship. Table 1. Total Number of Patients Seen by Clinic, Alive or Deceased Status, and Average Years Between First Appointment and Death (N=29418) Clinic Total No. No. Alive Percent Alive No. Deaths PercentDeaths Avg Years from First Appt to Death Breast 11972 11219 94% 753 6% 4 GI 837 787 94% 50 6% 3 GU 4264 3952 93% 312 7% 4 Gyn 1284 1175 91% 109 8% 4 Head & Neck 2763 2482 90% 281 10% 3 Lymphoma 759 707 93% 52 7% 4 Melanoma 1234 1174 95% 60 5% 3 Sarcoma 87 85 98% 2 2% 1 Stem Cell Transplant 3141 1917 61% 1224 39% 1 Thoracic 489 461 94% 28 6% 2 Thyroid 2588 2516 97% 72 3% 4 Citation Format: Katherine R. Ramsey, Patricia H. Chapman, Guadalupe R. Palos, Maria A. Rodriguez. Mortality patterns among cancer survivors receiving care in dedicated survivorship clinics [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5258.

Femoral stem neck geometry determines hip range of motion shape : a computer simulation study.

AimsIn computer simulations, the shape of the range of motion (ROM) of a stem with a cylindrical neck design will be a perfect cone. However, many modern stems have rectangular/oval-shaped necks. We hypothesized that the rectangular/oval stem neck will affect the shape of the ROM and the prosthetic impingement.MethodsTotal hip arthroplasty (THA) motion while standing and sitting was simulated using a MATLAB model (one stem with a cylindrical neck and one stem with a rectangular neck). The primary predictor was the geometry of the neck (cylindrical vs rectangular) and the main outcome was the shape of ROM based on the prosthetic impingement between the neck and the liner. The secondary outcome was the difference in the ROM provided by each neck geometry and the effect of the pelvic tilt on this ROM. Multiple regression was used to analyze the data.ResultsThe stem with a rectangular neck has increased internal and external rotation with a quatrefoil cross-section compared to a cone in a cylindrical neck. Modification of the cup orientation and pelvic tilt affected the direction of projection of the cone or quatrefoil shape. The mean increase in internal rotation with a rectangular neck was 3.4° (0° to 7.9°; p < 0.001); for external rotation, it was 2.8° (0.5° to 7.8°; p < 0.001).ConclusionOur study shows the importance of attention to femoral implant design for the assessment of prosthetic impingement. Any universal mathematical model or computer simulation that ignores each stem’s unique neck geometry will provide inaccurate predictions of prosthetic impingement.Cite this article: Bone Joint Res 2021;10(12):780–789.

Modularity of total hip prosthesis and its tribological implications

PurposeThe study aims to analyze the fretting phenomenon, manifested at the taper junctions of modular total hip prostheses (THP). Modularity of prostheses implies the micro-movement occurrence. Fractures can arise as a result of the fretting cracking of the prostheses components, affecting durability of modular THPs. Fretting corrosion is associated with the decrease in the clinical acceptance of hip modular implants.Design/methodology/approachStarting from the fretting phenomenon influence on modularity, monoblock THPs and prostheses with modular femoral head recovered from some review surgeries were investigated. Modular prostheses have a taper junction femoral head – femoral stem neck. Investigation consisted in the analysis of fretting wear and fretting corrosion, of the femoral heads’ taper and of the femoral stems’ trunnions.FindingsThe main result was that the micro-movement that provokes the fretting of the femoral head-femoral stem taper junction analyzed does not have the same direction. It is manifesting in the direction of the axis of the femoral head taper, around this axis or as a composed movement. The authors suspect that this is due to the different design of the taper. In this way, the inclination of the stem’s trunnion into the head hole has a different angular misalignment and may cause greater damages of the taper.Originality/valueThis result can be a starting point from the improvement of the future taper junctions design that will improve the quality, durability and modularity of THPs.

Sistem Pakar Mendiagnosa Penyakit Bawang Merah Dengan Metode Depthfirst Search Backward Chaining

There were 12 disease data obtained from the agriculture and horticulture department of Deli Serdang, namely earthworms, thrips pests, leaf caterpillars, armyworms, aphids, root namhodes, purple spots, powdery mildew, stem neck rot, anthracnose, fusarium wilt, rot. poor, dead shoots (phytopthora porri foister) and there are 30 Symptoms of disease in onion plants An expert system is a computer program that provides expert advice (decisions, recommendations or problem solving) as if people had been consulted. The backward chaining method is the opposite of forward chaining which starts with a hypothesis (an object) and asks for information to convince or ignore. Backward chaining inference engines are often called Object-Driven/Goal-Driven. In this study, a web-based expert system was designed using the backward chaining method which aims to detect the type of disease in shallot plants by paying attention to the symptoms experienced in shallot plants. By using the backward chaining method, the value of disease certainty in shallot plants will be obtained from the expert system designed. The test results concluded that the design of an expert system for diagnosing diseases in shallots using the backward chaining method was as expected.

High Risk of Neck-liner Impingement and Notching Observed with Thick Femoral Neck Implants in Ceramic-on-ceramic THA.

Recently, impingement between the femoral stem and ceramic liner, which appears as a notch in the stem neck on radiographs, has emerged as a new complication. However, the proportion of impingement, potential risk factors, and related complications are poorly elucidated. In patients who underwent ceramic-on-ceramic (CoC) THA and had at least 10 years of follow-up, we asked: (1) What proportion had radiographic evidence of stem neck-ceramic liner impingement (notching of the stem), and what implant design, implantation factors, or complications such as ceramic fracture or metallosis are associated with impingement? (2) How common are the complications of noise and ceramic fracture? (3) What are the radiologic changes (including fixation of femoral and acetabular components, osteolysis, and heterotopic ossification) and clinical outcomes as determined by the modified Harris hip score (mHHS) for this cohort? (4) What is the survivorship with implant revision as the endpoint and with reoperation for any reason as the endpoint after CoC THA using a thick-neck stem design? Between May 2003 and April 2010, 643 patients underwent primary THA at a tertiary referral hospital. After excluding patients with metal-on-polyethylene and with ceramic-on-polyethylene implants, 621 patients were considered eligible for this study. All patients received the same hemispherical titanium cup, a standard-length tapered titanium stem, and a CoC bearing. Of those, 19% (115) were lost to follow-up before 10 years, and 8% (50) were excluded because they died before the minimum follow-up duration of 10 years, leaving 73% (456) for analysis. Patients had a mean age of 50 ± 14 years and were followed for a median (range) of 13 years (10 to 17). The mean cup abduction was 38° ± 5°, and the mean cup anteversion was 26° ± 7°. To determine the proportion of patients with the neck-liner impingement, we analyzed the plain radiographs of every patient during follow-up to detect notches around the stem. The detection of stem neck notches on the radiographs was reliable (intraobserver reliability: κ = 0.963; p < 0.001 and interobserver reliability: κ = 0.975; p < 0.001). To evaluate factors related to notching, we compared the possible confounding factors including gender, age, BMI, implant position, neck length, and head diameter. Complications such as ceramic fracture, noise, dislocation, and periprosthetic joint infection were recorded. Noise was evaluated via interview and with the Hip Noise Assessment Questionnaire, which assessed the noise qualitatively. For clinical outcome, we assessed the mHHS, which includes pain and function scales (0 [worst] to 100 [best]), every visit. Tilting of at least 4° or migration of at least 4 mm was the criteria for cup loosening; subsidence more than 3 mm, any change in position, or a continuous radiolucent line greater than 2 mm was the criteria for stem loosening. To evaluate osteolysis, we performed CT scans in 57% (262 of 456) of patients. Kaplan-Meier survivorship analysis was performed using the endpoints of survivorship free from implant revision and survivorship free from reoperation for any cause. The proportion of stem neck notching was 11% (49 of 456). There were no differences in cup abduction and anteversion between hips with notches and those without notches. Notched hips were more likely to have 28-mm than 32-mm heads (90% [44 of 49] versus 70% [285 of 407]; odds ratio 3.77 [95% CI 1.46 to 9.73]; p = 0.004). None of the 49 notched hips had a ceramic head or liner fracture or evidence of metallosis. A ceramic head fracture was reported in 2% (9 of 456); all fractures occurred in 28-mm short neck heads. A ceramic liner fracture occurred in 0.2% (1 of 456), and noise was noted in 6% (27 of 456). Acetabular osteolysis developed in 2% (7 of 456). The mHHS was 91 ± 12 points at the final follow-up. The survivorship free from implant revision was 97% (95% CI 96% to 99%), and the survivorship free from reoperation for any cause was 96% (95% CI 95% to 98%) at 13 years. The proportion of stems with neck-ceramic liner impingement and ceramic component fracture were unacceptably high after the use of a thick-neck stem design, especially when a 28-mm head was used. We have discontinued the use of this stem design and we recommend that such stems should not be used when CoC bearings are used. As these findings might be generalized to other bearing couples, further studies focused on polyethylene liner wear and local metallosis due to thick stem neck are warranted. Level III, therapeutic study.

Retrieval analysis of neck fracture on uni-modular total hip arthroplasty stems: The contributions of material processing and stem design.

Total hip arthroplasty stem fracture is an important contributor to morbidity rate and increases the cost of revision surgery. Failure is usually caused by issues related to overload, inadequate stem support, inappropriate stem design or dimensions and material processing. In this study, the role of the relationship between material characterization and biomechanical performance in the fracture of retrieved stems was explored. The stems were manufactured with forged stainless steel, had the same length, 12/14 trunnion, and 28-mm head. These stems were evaluated by macroscopic and microscopic examination to identify the causes of premature failure. Each stem was sectioned into four regions, and the cross-sections were used for the microhardness and grain size analysis. Finite element analysis (FEA) was carried out, considering the stem positioned at the femur, a musculoskeletal model, and biomechanical loading. All stems had fractured through a fatigue mechanism, mainly a unidirectional bending loading condition, with crack nucleation on the lateral side and propagation on the medial side. The numerical analysis revealed maximum mechanical stress on the lateral side of the stem neck, but this was below the yield stress calculated via the hardness. The use of a shorter head neck length could reduce the maximum mechanical stress at the neck. At a cross-section near the plane of the stem fracture, the hardness was lower than that normally reported by the ASM, and there were heterogonous and coarse grain sizes on the lateral side. The main cause of failure of the two stems analyzed was a combination of low hardness and coarse grain size, due to inappropriate materials processing, worsen by a high level of stress on the lateral side of the neck due to the large stem-head offset selected by the orthopedic surgeon.

A Modeling Study of a Patient-specific Safe Zone for THA: Calculation, Validation, and Key Factors Based on Standing and Sitting Sagittal Pelvic Tilt.

Lumbar-pelvic stiffness and sagittal imbalance have been reported to increase the risk of dislocation and wear after THA. One potential way to approach this concern is by identifying patient-specific safe zones for THA components based on the standing and sitting sagittal pelvic tilt. However, there is no algorithm to integrate the standing and sitting pelvic tilt into the surgical plan of component orientations. We established a new mathematical algorithm for determining a patient-specific safe zone for THA by integrating the impingement-free ROM requirements of standing and sitting while preventing edge loading while standing. We aimed to determine (1) the accuracy of this new method for predicting the impingement-free ROM for a given component orientation, (2) the sensitivity and specificity of detecting an impingement-free acetabular cup position for standing and sitting, and (3) the influences of key factors including pelvic tilt while standing and pelvic tilt while sitting and implant parameters on patient-specific safe zones. A strategy for calculating the intersection of standing and sitting impingement-free safe zones and the zone of a standing radiographic inclination of ≤ 45° was used to develop patient-specific safe zones. We conducted a computer simulation study including the pelvis and THA prosthesis to answer the three study questions. We enrolled 10 patients who underwent robot-assisted THA for avascular necrosis of the femoral head (mean age 49 ± 19 years; five were women) from October 2019 to December 2019. We used a prosthesis model with a conical stem neck and a non-hooded liner, with the femoral head diameter ranging between 28 mm and 40 mm, and the corresponding head-neck ratio ranging between 2.33 and 3.33. We tested 1680 movements for the accuracy of impingement-free ROM (Question 1), and 80 marginal points and 120 non-marginal points of the comprehensive impingement-free safe zone, which combines the standing and sitting postures (Question 2). For Question 3, we explored the influences of standing and sitting pelvic tilt, femoral head diameter, and ROM criteria on the size of the patient-specific safe zone. With the simulation method as a reference for detecting impingement, the mean absolute error (arithmetic mean of all the absolute errors) of the calculated impingement-free ROM was 1.4° ± 2.3°, and the limit of agreement of errors was between -3.6° and 3.7°. The sensitivity of detecting a safe cup orientation within the comprehensive impingement-free safe zone for a given ROM criterion was 98.9% (95% CI 93.6% to 99.9%), and specificity was 97.1% (95% CI 91.0% to 99.2%). There were no impingement-free safe zones for 29% (pelvic tilt combinations without an impingement-free safe zone and all tested combinations) and no patient-specific safe zones for 46% (pelvic tilt combinations without a patient-specific safe zone and all tested combinations) of the tested combinations of standing and sitting pelvic tilt. The patient-specific safe zone was sensitive to changes in standing and sitting pelvic tilt, femoral head diameter, stem version, and ROM criteria. Stem anteversions beyond 10° to 20° dramatically reduced the size of the patient-specific safe zone to 0 within a change of 10° to 20°. The patient-specific safe zone algorithm can be an accurate method for determining the optimal orientation for acetabular cups and femoral stems in THA. The patient-specific safe zone is sensitive to changes in standing and sitting pelvic tilt, stem version, ROM criteria, and the femoral head diameter. A narrow zone of 10° to 20° for stem anteversion is recommended to maximize the size of the patient-specific safe zone. This study suggests the potential of a mathematical algorithm to optimize the orientation of THA components and illustrates how key parameters affect the patient-specific safe zone.

THE CERAMIC MODULAR HEAD IMPROVEMENT IN THE DESIGN OF A TOTAL HIP REPLACEMENT

For the first time, a design of a modular ceramic ball head of a total hip joint replacement (THR) friction pair has been developed, which has the properties of a metal in conjunction with the stem neck and the properties of a ceramics on bearing surface of the pair. This is achieved by creating a low-cost, low-toxic, durable fixed connection of the head made of alumina or zirconia ceramics and the titanium-based alloy sleeve to obtain a brazed joint that is efficient in human synovial fluid. With the help of finite element analysis, a quantitative assessment of the strength and rigidity of the proposed head design was performed and its use in modern hip arthroplasty was indicated. The approbation of the proposed design solutions for creating a THR ceramic head with a titanium-based alloy sleeve brazed was carried out.

Minimum 15-year results of metasul 28-mm metal-on-metal total hip arthroplasty in patients younger than 50 years of age

BackgroundSome propitious mid- and long-term studies had been reported for MoM bearings; however, most studies have addressed specific patient groups rather than younger, active patients, who probably represent the most suitable population for investigations on wear and osteolysis. The purpose of this study to evaluate the long-term results of second-generation metal-on-metal cementless total hip arthroplasty (THA) in patients aged <50 years.MethodsFrom December 1997 to January 2004, primary THA using a metal-on-metal bearing cementless implant was performed in 63 patients (72 hips) aged <50 years. The mean follow-up duration was 18.6 (range, 15.9–22.1) years, and the mean age at initial operation was 39 (range, 22–49) years. Clinical results, complications, survivorship, osteolysis, and aseptic loosening were evaluated.ResultsThe mean Harris hip score and Western Ontario and McMaster Universities Arthritis Index scores were improved from 57.8 (range, 28–69) points and 73.4 (range, 63–94) points preoperatively to 91.7 (range, 80–100) points and 25.5 points (range, 17–38) points, respectively, at the last follow-up. Osteolysis lesions were found in 12 hips (acetabulum, 6 and femur, 6). The notching occurred on the femoral stem neck occurred in 12 hips. The mean serum cobalt and chromium concentrations were 2.3 (range, 0.2–10.6) μg/L and 1.7 (range, 0.4–8.1) μg/L, respectively, at a mean follow-up of 12.7 years in 32 patients (50.1%). The Kaplan-Meier survivorship curve analysis with revision for any reason as the endpoint revealed that 93.1% survived at 18.6 years’ follow-up.ConclusionsSecond-generation metal-on-metal cementless THA was found to produce satisfactory clinical and radiographic results with a low revision rate for osteolysis and aseptic loosening in patients aged less than 50 years.

Is Combined Anteversion Equally Affected by Acetabular Cup and Femoral Stem Anteversion?

BackgroundTo create a safe zone, an understanding of the combined femoral and acetabular mating during hip motion is required. We investigated the position of the femoral head inside the acetabular liner during simulated hip motion. We hypothesized that cup and stem anteversions do not equally affect hip motion and combined hip anteversion. MethodsHip implant motion was simulated in standing, sitting, sit-to-stand, bending forward, squatting, and pivoting positions using the MATLAB software. A line passing through the center of the stem neck and the center of the prosthetic head exits at the polar axis (PA) of the prosthetic head. When the prosthetic head and liner are parallel, the PA faces the center of the liner (PA position = 0, 0). By simulating hip motion in 1-degree increments, the maximum distance of the PA from the liner center and the direction of its movement were measured (polar coordination system). ResultsThe effect of modifying cup and stem anteversion on the direction and distance of the PA’s change inside the acetabular liner was different. Stem anteversion influenced the PA position inside the liner more than cup anteversion during sitting, sit-to-stand, squatting, and bending forward (P = .0001). This effect was evident even when comparing stems with different neck angles (P = .0001). ConclusionCup anteversion, stem anteversion, and stem neck-shaft angle affected the PA position inside the liner and combined anteversion in different ways. Thus, focusing on cup orientation alone when assessing hip motion during different daily activities is inadequate.

Cementless ceramic-on-ceramic total hip arthroplasty in post-traumatic osteoarthritis after acetabular fracture: long-term results.

Total hip arthroplasty (THA) is the standard procedure for post-traumatic osteoarthritis (OA) of the hip after acetabular fracture. However, it is not as simple as a primary THA, challenging the surgeon with anatomical deformity and intra and postoperative complications. In the current literature, there is a lack of studies reporting long-term results. May ceramic-on-ceramic (CoC) bearings provide good clinical and radiological outcomes at a long-term follow-up in patients undergoing THA following acetabular fracture? We retrospectively analyzed 68 patients (mean age 47years [range 22-75)] who underwent cementless modular neck stem THA, all implants CoC bearings (50 previously operatively treated and 18 non-operatively treated) after a specific CT study protocol at our Institute since 2000-2008. Clinical outcomes, prosthetic components' osseointegration, survival rate, and reasons for revision were analyzed. Minimum clinical and radiological follow-up was 10years. HHS improved significantly after surgery from 37.6 ± 14.1 to 88.4 ± 11.6. 8 revision surgeries were performed, none for infection: we reported 2 stem aseptic loosening, 2 periprosthetic femoral fractures and 4 modular neck fractures. One implant noise (third-generation ceramic coupling) was described. Cup osseointegration was present (according to Moore the presence of at least 3 radiological criteria defines an effective osseointegration) in 67 patients (98.5%). After a 10years follow-up, survival rate resulted 88.4%, sensibly higher than most of results reported in the current literature. The high survival rate may be related to CoC: no osteolysis and no infections were reported. Also acetabular cup loosening incidence was sensibly lower (1.47%) among loosening rate described by other authors. Clinical and radiological outcomes were decent, probably due to modular prosthesis design. Modular necks are a solution which can help achieving a proper functional reconstruction of the hip (offset, center of rotation), but should be avoided in young and overweight patients because of the high risk of fracture. CoC bearings in THAs in post-traumatic OA after acetabular fracture showed good results despite the fact that specific ceramic-related issues have to be considered.

Unexpected varus deformity and concomitant metal ion release and MRI findings of modular-neck hip stems: descriptive RSA study in 75 hips with 8 years’ follow-up

Background and purpose — Modular-neck hip stems have been identified with corrosion-related problems from the neck–stem junction. We report an ongoing varus deformity of modular-neck hip stems with simultaneous metal ion release observed during a study comparing the migration of modular vs. standard hip stems. Patients and methods — We followed 50 patients with modular and 25 with standard neck stems using radiostereometry (RSA). At 5-year follow-up, we noted a compromised integrity of the modular stem with varus deformity in the neck–stem interface. Changes in head–tip distance as well as whole-blood ion concentration and MRI findings were analyzed. The modular stems were followed further up to 8 years. Results — The head–tip distance decreased continuously by 0.15 mm per year resulting in 1.2 (95% CI 1.0–1.4) mm at 8 years for modular stems, while for the standard stems at 5 years, the decrease was 0.09 (CI 0.0–0.2) mm or 0.02 mm/year. For the modular stems, the reduction in head–tip distance correlated to the increase in whole-blood cobalt concentration at 8 years but not to the MRI grading of tissue reactions. At 5 years, cobalt levels were 4.9 µg/L for modular stems and at 8 years 4.8 µg/L, whereas for standard stems this was 1.0 µg/L. After 8 years, 9 of 72 stems had been revised for different reasons, but only 1 with obvious adverse local tissue reaction (ALTR). Interpretation — We present a surprisingly large progressive deformation at the modular neck–stem junction, but so far without a definite clinical problem. Even the femoral head seems to show slight compression onto the taper over time. A high rate of revisions for the modular type of this stem has raised general concerns, and it has been recalled from the market.

The effect of varus stem placement on joint offset during total hip arthroplasty: a virtual study.

With total hip replacement (THR), varus alignment of an uncemented stem will increase offset which can have significant detrimental effects on muscular balance, leg length and overall satisfaction. Thus, we used 3D planning software to determine the change in joint offset with increasing varus stem placement. Eight patients undergoing THR had routine computed tomography (CT) scans to allow for 3D hip planning. Each set of CTs was templated with a straight stem and an uncemented acetabular cup. Initial templating was performed to reproduce native leg length and offset. The templated stem was then rotated into varus at 1° intervals, up to 6° varus while offset changes for all varus positions were noted. This was repeated for each of 3 neck angles, 125°, 135° and 135° lateral and for each stem sizes 1, 3, 5 and 7. Overall, there was a mean 1.5 mm increase in offset for every 1° of varus. The stems with a 125° neck angle had the greatest increase in mean offset at 1.6 mm for every 1° of varus. The stem neck angles of 135° lateral offset and 135° standard offset, had a mean increase in offset of 1.5 mm and 1.4 mm respectively for every 1° of varus. A greater mean increase in offset for every 1° of varus was observed with increasing stem size. We have quantified the relationship between alignment and offset with every 1° of varus placement increasing hip offset for straight stems by 1.5 mm. This can be used as a guide for surgeons during THR so that they have a better quantitative understanding of how varus placement of the stem affects the hip offset.

Comparison of 127° small and 135° large stem angle prostheses in total hip arthroplasty

To investigate the effect of total hip arthroplasty(THA) with the prosthesis of 127° small neck stem angle and 135° large neck stem angle. From January 2014 to June 2016, 84 patients with THA were selected, including 44 males and 40 females, aged 45 to 72(53.4±8.1) years old, 68 patients with necrosis of the femoral head(32 on the left and 36 on the right), 16 patients with serious osteoarthritis of the hip caused by other reasons, and the course of disease was 9 to 36 (24.0±5.5) months. Forty-two patients in each group were evaluated by Harris score, visual analog score(VAS), length measurement of lower limbs, biomechanical evaluation of different angles of the neck stem. The complications and quality of life 24 months after operation were compared. Two patients in each group were lost, the rest were followed up for 30 to 36 (33.0±1.6)months. The Harris score and the length of both lower limbs were measured before and 1, 6, 12, 24 months after operation. The difference of Harris score and the length of both lower limbs in the two groups was significantly improved compared with that before operation(P<0.05), but there was no significant difference between the two groups(P>0.05). There was no significant difference between the two groups in VAS score before operation (P>0.05), but the VAS score of the group with large neck stem angle was significantly lower than that of the group with small neck stem angle(P<0.05). There was no significant difference in the incidence of postoperative complications between the two groups (P>0.05). The quality of life of the patients in the two groups after 24 months was significantly higher than that before operation (P<0.05). THA with large and small neck stem angle prosthesis can better recover the function of hip joint, but large neck stem angle can reduce the degree of postoperative pain and improve the quality of life of patients.

Treatment of proximal humeral fractures in elderly patients with intramedullary nail and locking plate

Objective: To compare the effect of intramedullary nail and locking plate in the treatment of proximal humeral fractures in the elderly. Methods: A total of 37 elderly patients with proximal humeral fractures were selected from April 2016 to June 2018 in Tianjin Hospital, including 13 males and 24 females, aged (66±5) years. The patients were divided into observation group (17 cases) and control group (20 cases) according to the random number table, and were treated with multiloc intramedullary nail and locking plate respectively. The operation time, blood loss, healing time of fractures, visual analogue scale of pain, Neer shoulder function score were recored and compared between the two groups. The data were compared with t test between the two groups. Results: The operation time of the observation group was shorter than that of the control group ((72±7) min vs (89±9) min, t=6.365, P<0.05); the intraoperative bleeding volume was lower than that of the control group ((56±6) ml vs (74±8) ml, t=7.923, P<0.05). The superior rate of shoulder function was 94.1%(16/17) in the observation group and 90.0%(18/20) in the control group (χ(2)=0.209, P>0.05). The VAS score of the observation group was lower than that of the control group on the first day after operation (t=4.706, P<0.05); the Neer shoulder function score of the observation group was higher than that of the control group on the sixth month after operation (81±8 vs 76±8, t=2.156, P<0.05). Six months after the operation, the valgus angle (19.21°±2.88°) of the observation group was larger than that of the control group (16.32°±2.63°, t=3.189, P<0.05), the humeral head varus angle (3.57°±0.47°), the humeral neck stem angle (139°±10°) was smaller than that of the others (5.24°±1.26°), (146°±13°) (t=5.159, 2.258, both P<0.05). There was no significant difference in shoulder function score and complication rate 12 months after operation between the two groups (both P>0.05). Conclusion: Both intramedullary nailing and locking plate can achieve better results in the treatment of proximal humeral fractures in the elderly, but the operation time of intramedullary nailing is shorter, the pain after operation is lighter and the recovery is faster.

Taper corrosion: a complication of total hip arthroplasty.

The focus on taper corrosion in modular hip arthroplasty increased around 2007 as a result of clinical problems with large-head metal-on-metal (MoM) bearings on standard stems. Corrosion problems with bi-modular primary hip stems focused attention on this issue even more.Factors increasing the risk of taper corrosion were identified in laboratory and retrieval studies: stiffness of the stem neck, taper diameter and design, head diameter, offset, assembly force, head and stem material and loading.The high variability of the occurrence of corrosion in the clinical application highlights its multi-factorial nature, identifying the implantation procedure and patient-related factors as important additional factors for taper corrosion.Discontinuing the use of MoM has reduced the revisions due to metal-related pathologies dramatically from 49.7% (MoM > 32 mm), over 9.2% (MoM ⩽ 32 mm) to 0.8% (excluding all MoM).Further reduction can be achieved by omitting less stiff Ti-alloys and large metal heads (36 mm and above) against polyethylene (PE).Standardized taper assembly of smaller and ceramic heads will reduce the clinical occurrence of taper corrosion even further. If 36 mm heads are clinically indicated, only ceramic heads should be used.Taper-related problems will not comprise a major clinical problem anymore if the mentioned factors are respected.Cite this article: EFORT Open Rev 2020;5:776-784. DOI: 10.1302/2058-5241.5.200013

First report of Rhizoctonia solani AG-4 HGI Causing Stem Canker on Fagopyrum tataricum (Tartary buckwheat) in China.

Tartary buckwheat (Fagopyrum tataricum) is an ideal functional food source, which is well known to be gluten-free and rich in proteins, fats, vitamins, minerals, and flavonoids of various pharmaceutical uses, such as rutin, quercitin and epicatechin (Zhou, M et al. 2018). The Rhizoctonia solani AG-4 HGIII causing severe canker disease was first isolated from common buckwheat (F. esculentum) in Inner Mongolia of China (Zhou, H et al. 2015). In 2018, sunken lesion and dark brown symptoms were observed on the root and stem of ten days old Tartary buckwheat in Liangshan (28°21'N, 103°19''E), Sichuan Province and Fenghuang (28°19' N, 109°48' E), Hunan Province in China. In the beginning, water soaked spots appeared on the stem base, where gradually became rotten and necrotic, finally resulting in the damping-off and death of buckwheat seedlings. This disease had over 40% incidence and lead to serious losses to the buckwheat production in 2018. To isolate the pathogens on Tartary buckwheat, ten plants with typical symptoms were collected from each location. The infected tissue was taken and cut into 3mm pieces from the margin between healthy and diseased tissue, surface sterilized with 1% sodium hypochlorite solution for 4 min, washed three times with sterile distilled water, dried on sterilized filter paper and then placed on potato dextrose agar (PDA) with 100 mg/ml streptomycin sulfate. After incubation at 28℃ in the dark for 2 days, mycelial tips of four fungal cultures were transferred to PDA plates for purification. Initially, colonies were pale white, and then turned brown after 2 days incubation. The mycelium was hairy and concentrically whorled in the culture medium. Microscopic observation showed that the hyphae characteristically branched at right angles and had constriction at the base of hyphal branches. Nuclear staining showed that the hyphae cells were multinuclear. These morphological features revealed that the isolates belonged to R. solani (Sneh et al. 1991). Subsequently, the ribosomal DNA (rDNA) internal transcribed spacer (ITS) region of one isolate was amplified by PCR (White et al. 1990) and sequenced (GeneBank accession no. MT078642) by Shanghai Majorbio Bio-pharm Technology Co.,Ltd. DNA was extracted by Fungal genomic DNA Extraction Kit, D3390-02, OMEGA. The BLAST similarity analysis showed a 99.96% match with R. solani AG-4 HGI (GenBank accession no. JQ343830) and 99.85% identity to R. solani AG-4 HGI isolate SX-8 (GenBank accession no. KJ170346) (Suli, Sun et al. 2015). Furthermore, the phylogenetic analysis performed by the neighbour-joining method (MEGA 7 software) showed that the isolate was clearly clustered with the group of R. solani AG-4 HGI (Ireland et al. 2015). Pathogenicity was tested in the greenhouse condition to satisfy Koch's postulates. Tartary buckwheat plants of seven days old and fifty days old were respectively inoculated near the base of the stem neck with one mycelial plug contacted directly. Ten plants in a pot were inoculated as one treatment, four pots were used for replicates. Control plants were inoculated with PDA medium plugs without fungi. All the plants were kept at 26℃ with 14 h light, 10 h dark and 96% humidity. After five days (Suli, Sun et al. 2015), over 90% of the inoculated plants exhibited necrotic brown lesions on stems that was similar to those symptoms observed in the field, whereas control plants remained asymptomatic. The visible characteristics and ITS sequence of the pathogen re-isolated from symptomatic plants were in accordance with the original isolate (R. solani AG-4 HGI). Based on disease symptoms in the fields, morphological characteristics, ITS sequence analysis, and pathogenicity assay, we concluded that R. solani AG-4 HGI was the principle cause of Tartary buckwheat blight in Liangshan, Sichuan Province and Fenghuang, Hunan Province in China. Previously, R. solani AG-4 HGI has been identified as a Chinese chive pathogen (Shi, Y et al. 2017). To the best of our knowledge, this is the first report of the natural occurrence of Rhizoctonia solani AG-4 HGI affecting Tartary Buckwheat in China. This finding is helpful for the early diagnosis and identification of the disease, which will be the guiding of effective control methods to the devastating disease at the early stage.

Five-Year Follow-Up of Clinical Outcomes with an Anatomic Dual-Mobility Acetabular System: A Multicenter Study.

BackgroundThe dual-mobility implant system has been shown to increase impingement-free range of motion and decrease dislocation risk by increasing the effective head size. In addition, the anatomic dual-mobility (ADM) cup offers relief between the acetabular shell rim and the iliopsoas tendon. This study was designed to review a series of hips implanted with the ADM acetabular cup to examine clinical outcomes after 5 years of implantation at multiple orthopaedic centers.MethodsWe retrospectively queried our prospectively collected total joint arthroplasty registry for patients who underwent total hip arthroplasty with an ADM cup from January 2008 to December 2012 at 4 different orthopaedic institutions and who had minimum 5-year follow-up. Harris Hip Scores and visual analog scale scores were evaluated. Postoperative complications, dislocations, and revisions for any reason were recorded.ResultsA total of 142 patients had a mean follow-up of 5.7 years (range: 5.0 to 8.0 years). Radiographic analysis showed no radiolucent lines, osteolysis, or acetabular loosening. There were no dislocations in this patient series. Two (1.2%) hips required a revision because of adverse local tissue reactions related to corrosion from a recalled modular neck stem, but this was unrelated to the ADM cup. The mean Harris Hip pain scores increased from 17 points preoperatively to 39 points at the most recent follow-up (P < .001). The mean Harris Hip function score increased from an average of 29 points preoperatively to 38 points at the most recent follow-up (P < .001). The mean visual analog scale score showed patient improvement from 6.5 preoperatively to 1.2 postoperatively (P < .001).ConclusionsADM prostheses were designed to reduce the risk of dislocation by increasing the size of the effective femoral head. In this multicenter study of ADM cups used in primary total hip arthroplasty, we demonstrated good clinical and radiographic outcomes, no dislocations, and no revisions at midterm 5-year minimum follow-up. Patient-reported outcome measures were also improved, supporting the use of this implant.